1. Field of the Invention
The present invention relates to a thermal printer that uses a thermal paper sheet having heat-sensitive layers on both surfaces thereof, and a method of controlling the same.
2. Description of the Related Art
A thermal paper sheet used in a thermal printer has a heat-sensitive layer on one surface thereof. In accordance with this structure, a thermal printer has one thermal head, and prints printing data input from the outside on one surface of a thermal paper sheet by using the single thermal head. The printed thermal paper sheet is cut by a cutter and provided to a user.
When an amount of printing data input from the outside is large, a thermal paper sheet on which the data is to be printed becomes long and hence it is difficult to handle by a user.
On the other hand, a thermal paper sheet having heat-sensitive layers on both surfaces thereof has been recently developed. When this thermal paper sheet is used and printing data is divided and printed on both surfaces of the thermal paper sheet, the length of the thermal paper sheet provided to a user can be reduced, which saves thermal paper.
In order to print data on both surfaces of the thermal paper sheet, there is required processing of, e.g., feeding a paper sheet to an image forming portion of a photosensitive drum or a development unit to form an image on a surface of the paper sheet, returning the paper sheet having the image formed thereon to the image forming portion while reversing the paper sheet, and forming an image of a rear surface of the paper sheet by the image forming portion, like double-side copying in a copying machine (see, e.g., Jpn. Pat. Appln. KOKAI Publication No. 233256-1997 and Jpn. Pat. Appln. KOKAI Publication No. 24082-1994).
However, processing similar to that used in a copying machine takes too much time, and therefore cannot be applied to a thermal printer used for issuing a sales receipt to a customer at, e.g., a store.